Morphogenesis in wing imaginal discs: its relationship to changes in the extracellular matrix.

An extracellular matrix (ECM) lies between the upper and lower epithelial layers of the wing imaginal discs of moths. Organization and composition of this extracellular matrix, as revealed by staining with ruthenium red, tannic acid, and alcian blue, changes in concert with levels of hormones in the haemolymph. The ECM of the wing imaginal disc is an environment for cellular movements. Reorganization of the matrix and increase in ecdysteroid level is coupled with the proximal----distal migration of tracheal cells as well as the distal----proximal outgrowth of sensory neurons.